The present invention relates in general to the art of earth boring and, more particularly, to a rotary rock bit with an improved sealing system. The present invention is especially adapted for use on that type of rotary rock bit popularly known as a three cone rotary rock bit; however, its use is not restricted thereto and the system of the present invention can be used in other earth boring bits wherein an improved sealing and bearing system is needed.
A three cone rotary rock bit is adapted to be connected as the lower member of a rotary drill string. As the drill string is rotated, the bit disintegrates the formations to form an earth borehole. The three cone rotary rock bit includes three individual arms that extend angularly downward from the main body of the bit. The lower end of each arm is shaped to form a bearing pin or spindle. A rolling cone cutter is mounted upon each bearing pin and adapted to rotate thereon. The cone cutters include cutting structure on their outer surfaces that serves to disintegrate the formations as the bit is rotated.
The rotary rock bit must operate under very severe environmental conditions and the size and geometry of the bit is restricted by the operating characteristics. At the same time, the economics of petroleum production demand a longer lifetime and improved performance from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters thereby providing a longer useful lifetime for the cone cutters. This has resulted in the bearing and sealing systems being generally the first to fail during the drilling operation. Consequently, a need exists for improved bearing and sealing systems to extend the useful lifetime of the bit.
One of the problems encountered with radial seals in rock bits is that when the bearing is loaded the seal sees unequal squeeze on the top and bottom of the bearing pin. This will tend to knead the seal as the cutter rotates as well as cause leaks at the top where squeeze is minimum when the bit is loaded. The present invention minimizes this condition and promotes greater seal life. It improves bit performance by causing the seal to run concentrically during drilling.